1. Field of the Invention
The present invention relates to a high-frequency module mounting structure suitable for high-frequency modules, such as an on-vehicle electronic unit or a transmission unit for a mobile phone.
2. Description of the Related Art
Referring now to the drawings showing a high-frequency module mounting structure in the related art, FIG. 4 is a side view showing a high-frequency module mounting structure in the related art, FIG. 5 is an enlarged cross sectional view showing a principal portion of the high-frequency module mounting structure in the related art, and FIG. 6 is the high-frequency module mounting structure in the related art, showing a bottom view of a high-frequency module.
Referring now to FIG. 4 to FIG. 6, the high-frequency module mounting structure in the related art will be described below. A square circuit board 51 formed of a printed board is formed with a wiring pattern (not shown) on one side, and the circuit board 51 is provided with electric components 52, such as a IC part, a chip capacitor, and a chip resistance, in a state of being connected to the wiring pattern, so that a desired electric circuit is formed.
The lower surface of the circuit board 51 is provided with a plurality of electrodes 53 for connecting to an external circuit, as shown in particular in FIG. 6. The electrodes 53 are connected to the wiring pattern via a through hole (connecting conductor) so as to be capable of surface mounting, though it is not shown in the figure.
The electrodes 53 are disposed along four sides of the circuit board 51 by plural number each, and includes first and second electrode groups 54a and 54b disposed along opposed pair of sides respectively and third and fourth electrode groups 55a and 55b disposed along another opposed pair of sides respectively.
A box-shaped cover 56 formed of a metal plate is attached to the circuit board 51 by a suitable measure, such as soldering, so as to cover one side of the circuit board 51.
The cover 56 shields the electric component 52 and the wiring pattern electrically to form a high-frequency module M2.
A motherboard 61 constructed of the printed board is formed with a wiring pattern 62, and a plurality of lands 63 are disposed at predetermined positions of the wiring pattern 62 corresponding to the electrodes 53 of the high-frequency module M2.
The high-frequency module M2 is disposed on the motherboard 61, and the plurality of electrodes 53 and the plurality of lands 63 are soldered 64, so that the high-frequency module M2 is connected to the wiring pattern 62 that is the external circuit provided on the motherboard 61, and the high-frequency module M2 is attached to the motherboard 61.
The electrodes 53 and the lands 63 are soldered using cream solder or by Ball Grid Array (connection by means of metallic balls).
The high-frequency module mounting structure in the related art has a problem in that solder 64 is liable to be peeled because of shrinkage of the circuit board 51 or the motherboard 61 under the environmental influence because soldering is made only between the electrodes 53 on the high-frequency module M2 and the lands 63 on the motherboard 61, and thus reliability is not sufficient.